The present invention relates to a thermal spray powder and a method for forming a thermal spray coating.
In the field of fabricating semiconductor devices or liquid crystal devices, it is common to conduct microfabrication by plasma etching, which is one type of dry etching, using a reactive ion etching apparatus. Therefore, in semiconductor device fabrication apparatuses and liquid crystal device fabrication apparatuses, a member which is exposed during the etching process to the reactive plasma may suffer from erosion (damage). If particles are generated from a member in the semiconductor device fabrication apparatus or liquid crystal device fabrication apparatus by plasma erosion, the particles can deposit on the silicon wafer used in a semiconductor device or the glass substrate used in a liquid crystal device. If the amount of deposited particles is large or if the particles have a large size, the microfabrication cannot be carried out as designed, whereby the device yield decreases and quality defects occur, which can cause the device costs to increase.
In view of this, conventionally plasma erosion of members that are exposed to reactive plasma during an etching process has been suppressed or prevented by providing a ceramic thermal spray coating on the members (see, for example, Japanese Laid-Open Patent Publication No. 2002-80954). However, conventional thermal spray coatings do not sufficiently satisfy the required performance concerning plasma erosion resistance, and thus there still remains the need for improvements.
In the Examples of Japanese Laid-Open Patent Publication No. 2002-80954, the etching rate is 2 to 3 nm/min. The etching conditions obtainable with such an etching rate have a low plasma output (plasma power density) of at most about 200 W (0.6 W/cm2) (see KITAMURA et al., “Plasma-Erosion Properties of Ceramic Coating Prepared by Plasma Spraying”, Materials Transactions, The Japan Institute of Metals, Vol. 47, No. 7, pages 1677 to 1683, 2006). In contrast, in current etching processes for semiconductor device fabrication apparatuses and liquid crystal device fabrication apparatuses, to shorten the etching process time, the plasma output is generally set at 1,000 W or greater and the plasma power density set at 3 W/cm2 or greater. The thermal spray coating of Japanese Laid-Open Patent Publication No. 2002-80954 does not sufficiently satisfy the required performance concerning plasma erosion resistance under such tough etching conditions.